The present invention relates to water well drilling apparatus and, in particular, to an improved cutting head for replaceable mounting to a drill stem of a cable tool type drilling rig. A hardened, wedged cutting surface and outer, flattened arcuate reaming surfaces tapering upward about the bit's circumference from the cutting edge displace the soil/rock slurry to channels in the drill stem. A non-hardened upper end facilitates replacement welding to a prepared drill stem.
Drilling in the earth can be effectuated with a variety of equipment, the selection of which depends upon a variety of factors from the types of soil to the required hole size to the bore depth, to name a few of the variables. Most prevalent of all types of well drilling activity is that undertaken in search of water, where wells may have to be sunk from a few feet to thousands of feet. Most typically though the average well for residential and light commercial use consists of a well 4 to 6 inches in diameter sunk to a depth of 100 to 500 feet.
Two of the primary drilling methodologies historically used to sink such wells operate either on a continuous rotary or a repetitive-driving principle. The latter methodology generally employs a gantry tower which supports a plurality of pulleys and about which is trained a suitable length of cable. Suspended from the lowermost end of the cable is a weighted drive head which is used to drive a bore hole pipe liner and/or an elongated drill stem and to a lower end of which is mounted a suitable cutting tip or bit. The latter apparatus is commonly referred to as a cable tool drilling rig and U.S. Pat. No. 2,833,120 generally discloses one such rig.
Such apparatus when used for boring, generally operates to repetitively lift the drill stem to an upper extreme and from which the stem is allowed to free fall to strike the ground causing a cutting action at the tip. Inherent twist in the cable also causes the cutting tip to rotate slightly as it is driven into the soil. Repetitive drill action pulverizes the soil/rock to form a slurry which is vented from the bore hole via longitudinal reliefs let in the drill stem wall. The slurry is partially removed during drilling as the drill stem is periodically raised but otherwise partially lubricates the ongoing process.
Depending again upon the type of soil conditions, the rate at which the soil is drilled will vary. Although a variety of differently configured drill tips may be used, depending on the drilling conditions, ever changing soil conditions over the course of a single bore hole may mean multiple, time-consuming tip changes which are preferably to be avoided. An all-purpose drill tip is accordingly desired which facilitates drilling through soft, hard and rocky soils.
To the extent Applicant is aware of drill tip constructions, U.S. Pat. Nos. 50,949 and 2,927,773 disclose two types of porous, shallow well drill tips of a conical construction. These latter tips are typically sunk with the casing, which is driven much in the fashion of a fence post, and are intended to remain buried in the soil.
Applicant is also aware of a pair of wedge-shaped, rock shattering tips which are disclosed in U.S. Pat. Nos. 2,136,596 and 3,403,443. Again, the latter tips are intended more for shattering hard formations. Other tip constructions intended for similar uses are shown in U.S. Pat. No. 3,194,328 and wherein a number of tips including intersecting wedged cutting edges are disclosed which generally provide for four cutting surfaces which radiate from the center of the tip, when viewed end-on.
Applicant is also aware of a number of circular-shaped tips and drill stems which surround a annular center bore wherethrough the pulverized slurry is directed upwardly. These latter tips may be found upon directing attention to U.S. Pat. Nos. 1,647,239; 3,015,365; 3,280,925; and 3,837,414. Various of the latter tips also include one or more V-shaped teeth which extend from the annular periphery of the tip.
Depending too upon the tip construction and its mounting to the drill stem, it may be necessary to periodically re-sharpen the tip which effort may be rather time consuming or require special equipment, depending upon the tip's geometric shape. In some instances the tip may have to be re-forged completely, for example via hard surface welding/grinding techniques. Otherwise, where the tip is threadably coupled to the drill stem, the tip may be periodically replaced with sharpened bits which are sharpened during slack time. Preferably therefore, a tip is described hereinafter which in lieu of a threaded mounting might be cut from the drill stem with a replacement rewelded to the stem at the job site, all in a matter of minutes.